Digital Libraries will be one of the main ways to access structured information through the Internet. Information related to resources or objects is known as metadata. Several metadata models have been proposed; however, the model proposed by the Dublin Core Metadata Initiative (DCMI) has demonstrated great utility in digital libraries. The simplicity and generality of DCMI has facilitated the deployment of digital libraries and their interoperability. This paper proposes DCMI as metadata model in our own Digital Library Architecture (Biblioteca Digital de Nueva Generación -BDNG). We have extended DCMI and used some elements of DC-Library application profile (DC-Lib) in addition to new elements not previously considered. This paper presents the metadata models for the following applications: digital library of EAFIT University (BDEeafit), integration of digital or referential libraries (BDMetaLib) and digital library for E-Learning systems (BDEI). This paper also describes the general architecture of BDNG.